In the packaging of liquid products in containers fitted with threaded metal closures, a need commonly arises for protecting the thread area against exposure to the packaged product. This need stems in part from the susceptibility to damage at the interengaged threaded surfaces due to product attack and in part from the adhesive character of certain products which penetrate the interengaged threaded surfaces making thread disengagement difficult.
Those prior art metal closure concepts, designed to provide a liquid tight seal at the inner or terminal end of the thread interengagement, have lacked sufficient practicality to warrant commercial exploitation. For example, one known concept employs some type of protruding seat for supporting a gasket at the terminal end of the opening thread against which the leading portion of the closure member seals. Such arrangements, however, are costly to produce and do not readily lend themselves to accepted manufacturing practices. Another approach is to include an additional separately attachable part in the closure construction to perform the above described thread gasketing function. This arrangement is similarly undesirable from a cost standpoint.